1. Field of the Invention
The present invention relates to an image processing apparatus, a method of controlling an image processing apparatus, a program, and a storage medium that allow dealing with sheet fingerprint information (hereinafter also referred to as sheet fingerprint).
2. Description of the Related Art
A sheet is formed of interwoven fibers having a width on the order of 20 to 30 micrometers. The interwoven fibers form a random pattern. Such a random pattern is unique to each sheet, similar to fingerprints. Such a random pattern on a sheet is referred to as sheet fingerprint information.
Since sheet fingerprint information is unique to each sheet, by registering that “the original that I issued is a sheet having this specific sheet fingerprint information, this can be used conveniently to later determine whether a sheet is the “original” or a “fake.” The term “fake” includes a “copy of the original.”
According to techniques disclosed in Japanese Patent Laid-Open No. 2004-112644, when creating an original, with reference to a mark attached on a sheet of the original, an area having a predetermined distance from the mark as a reference position is defined as a sheet-fingerprint-information obtaining area. Furthermore, according to the techniques disclosed in the document, sheet fingerprint information is obtained from the defined sheet-fingerprint-information obtaining area. Furthermore, according to the techniques disclosed in the document, the sheet fingerprint information is encoded to generate an encoded image, and the encoded image is printed on the sheet of the original.
Furthermore, according to the description in paragraph 58 of Japanese Patent Laid-Open No. 2005-038389, it is desired to determine a range of a recording sheet where toner or the like is not attached on the basis of print data, and to define a sheet-fingerprint-information obtaining area in the range.
When a sheet-fingerprint-information obtaining area is defined according to the techniques disclosed in Japanese Patent Laid-Open No. 2004-112644, a flat black area, from which it is not possible to obtain sheet fingerprint information, could be defined as a sheet-fingerprint-information obtaining area. It is an issue to be addressed that a flat black area, from which it is not possible to obtain sheet fingerprint information (or comparison fails even if sheet fingerprint information is obtained), could be defined as a sheet-fingerprint-information obtaining area.
When a sheet-fingerprint-information obtaining area is defined according to the techniques disclosed in Japanese Patent Laid-Open No. 2005-038389, a completely white area could be defined as a sheet-fingerprint-information obtaining area. A completely white area could be cut out by a malicious third party and attached to another sheet. When this happens, the another sheet is recognized as the original.